1. Field of the Invention
The present invention relates to the field of sample injection equipment, and more particularly to sample injection equipment which may be used in high pressure liquid chromatography and similar fields.
2. Prior Art
The preferred embodiment of the present invention is directed toward the field of high pressure chromatography, and accordingly the prior art relating specifically thereto shall be described, it being understood however, that the present invention is not to be so limited as it may be readily used for other purposes such as UV spectriphotometric instrumentation and gas chromotography.
In high pressure chromatography, separating columns are first prepared having a special sorbent material therein for removing selected organic compounds from a sample passed therethrough. Such separating columns with various sorbent materials therein are commercially available from Analytichem, the assignee of the present invention. In the prior art, the separating columns characteristically are metal tubes of some form having a fixed filter at each end to confine the special sorbent therein against the relatively high pressure to which they will be subjected. To test for a particular material, a sample is first passed through the sample column to retain the selected organic material thereon, thereby effectively concentrating the material to be tested for. Thereafter the sample column is placed in the high pressure system, and the sample removed with an appropriate solvent under high pressure to carry the sample to the chromatograph. Such systems and testing are well known in the prior art, being commonly used in medical and other applications. However, heretofor the preparation and evaluation of the samples was generally a manual task requiring substantially constant attention of an operator, and providing all of the normal opportunities for operator error, including nonuniformities in the test method and/or the misidentification or intercontamination of samples.
Various methods and apparatus have been proposed to at least partially automate chromatographic testing, such as disclosed in U.S. Pat. No. 3,583,230 entitled "Sample Injection Method and Apparatus". In accordance with that patent, injector cartridges having filter material are placed in receiving holes around the periphery of a rotating turn table after a sample has been centrifuged into the filter material and the sample is filtered during the centrifuging. The sample within the cartridge is preeluted and then the turn table is rotated sequentially positioning the cartridges beneath an extendable and retractable loader which engages the cartridge. Desired zones of the chromatographic spectrum of the preeluted sample are injected through a capillary outlet in the cartridge into a chromatographic system. The cartridges themselves are individual cartridges having an elongated housing of plastic or other suitable material with a chamber or elongated channel formed centrally therein, lined with a tubular support column of glass or suitable plastic material for supporting the chromatographic absorptive filter material. That system has the advantage of providing automatic sealing on the cartridge wherein a plurality of samples can automatically and sequentially injected into a chromatographic system in such a manner that the chromatographic column apparently can be used continuously without regeneration. However, because the sample cartridges are individual sample cartridges, operator attention is required for the loading and unloading of the individual cartridges, with the attendant opportunities for misidentification of test results as a result thereof.
U.S. Pat. No. 3,996,017 discloses a cassette separating column system for chromatography wherein each cassette-like device contains a separating column with appropriate coupling means at each end thereof for connection to complimentary shaped fittings in a fluid tight manner. A special connection fitting allows the direct connection of the conical coupling surfaces to two column-containing cassettes simultaneously, though as before, each cassette itself only contains a single column, whereby each individual cassette and therefore each individual column would require manual loading, also with the same opportunity for confusion of samples.
Finally, U.S. Pat. No. 3,860,393 entitled "Automated System for Identifying Traces of Organic Chemical Compounds in Aqueous Solutions" discloses a system wherein a single sample may be automatically analyzed to identify traces of organic chemical compounds of different types. Here again, the system envisions a single sample containing column, even though multiple tests may be conducted on the sample.